In quantum physics, which effect produces a two-dimensional electron system with Hall resistance quantized in fractional values?

The fractional quantum Hall effect produces quantized Hall resistance at fractional values when a two-dimensional electron system is cooled to low temperatures and placed in a strong magnetic field.

Daniel Tsui, Horst Störmer, and Arthur Gossard discovered the effect in 1982 while studying electrons in a gallium arsenide heterostructure. Unlike the integer quantum Hall effect, its plateaus arise from strong interactions among electrons rather than mainly from single-particle energy levels.

The excitations of fractional quantum Hall states can carry fractional electric charge. The famous filling factor 1/3 state is associated with quasiparticles of charge e/3 in the idealized theoretical description.

The effect is a major example of emergent quantum behavior. Tsui and Störmer shared the 1998 Nobel Prize in Physics with Robert Laughlin, who explained the effect theoretically.